Method for providing an edge preparation on a cutting edge of a tool and a control and a processing machine for carrying out the method

ABSTRACT

A method for providing an edge preparation on a cutting edge of a tool by means of an edge processing operation includes clamping the tool in a processing machine for providing the edge preparation, recording as a reference value the position of the cutting edge to be processed by means of a sensor arranged on the processing machine, carrying out an edge processing operation by means of a preparation tool, recording the position of the cutting edge again by means of the sensor arranged on the processing machine and storing the position as an actual value, monitoring the edge processing operation on the basis of a comparison between the reference value and the actual value, and comparing the actual value with a desired value for material removed on the cutting edge.

BACKGROUND

1. Field of the Invention

The invention relates to a method for providing a defined edgepreparation on a cutting edge of a tool for machining metals by means ofa rounding operation, in particular for providing a defined edgepreparation on a drilling, reaming, threading and/or milling tool. Theinvention also relates to a control and to a processing machine forcarrying out the method.

2. Background Information

Both drilling and milling tools are produced, inter alia, in a pluralityof production steps from a rough round bar. In this case, modern highperformance tools are produced from solid carbide. In the process, thedesired geometry with main cutting edges is normally formed at the endface by a special point grinding method. In continuation of the tool,flutes with secondary cutting edges are often provided. The selection ofthe special point grinding, the configuration of the cutting edgegeometry and of the flutes depend on the respective requirements. Thecutting properties of the tool are considerably influenced by thecutting edge geometry. After the grinding operation, the cutting edgesare normally of very sharp design, and so the cutting edges areregularly rounded via “edge rounding”. This edge rounding, referred tobelow as rounding operation, is carried out using a suitable roundingtool, in particular by means of brushes. A high-precision roundingprocess is important here in order to achieve the desired cuttingproperties. The material removal is normally only within a range of afew um. A deviation from desired material removal leads to adeterioration in the cutting properties.

On account of the very hard material when using solid carbide drills,the brushes are subjected to high wear during the rounding operation,such that, during the processing of a multiplicity of tools, the resultof the rounding operation often varies in an undesirable manner at thesame machine settings.

A further conventional edge preparation in addition to such edgerounding is the provision of a bevel on a cutting edge. Here, too,reproducible high precision of the edge preparation is important.

Accordingly, a need exists for a simple, reliable method for producing adefined edge preparation, in particular during a multiplicity ofsuccessive edge processing operations, and for a processing machine forcarrying out this method.

SUMMARY OF THE INVENTION

The present invention addresses such needs by providing a method forproviding an edge preparation on a cutting edge of a tool by means of anedge processing operation, in particular for providing edge rounding ora bevel. Accordingly, for providing a defined edge preparation on acutting edge of a tool, in particular a drilling, reaming, threadingand/or milling tool, the tool is first of all clamped in place in aprocessing machine. The position of the cutting edge to be processed isthen recorded by means of a sensor arranged on the processing machineand is stored as a reference value. In the next method step, the edgepreparation operation is carried out by means of a preparation tool andthe position, which has then changed, of the cutting edge is thenrecorded again by means of the sensor and stored as an actual value.Finally, the edge preparation operation is monitored on the basis of acomparison between the reference value and the actual value and iscompared with a desired value for the material removal on the cuttingedge. As a result, the edge preparation is controlled overall in asimple and efficient manner.

In previous methods, it was regularly necessary for this purpose tocheck the result of the edge preparation in a complicated manner inseparate measuring devices. To this end, unclamping of the tool wasnecessary.

With the method now described herein, it is now possible to determinethe result of the edge processing operation directly at the machinetool, and therefore no separate measuring operation in a separatemeasuring device has to be carried out. The recording of the relativechange between the recorded reference value and the actual valuerecorded after the edge processing operation is especially important. Itis therefore not important to determine the actual absolute situationand position of the cutting edge in the coordinate system of theprocessing machine. As a result of the recording of the relative change,the material removal actually effected can be determined in a highlyprecise manner.

In this way, in particular online process monitoring is made possibleand provided by the simple measuring operation. Normally, a multiplicityof tools are processed one after the other on the processing machine andare subjected to the edge processing operation. The expression “onlineprocess monitoring” refers to the fact that, in the course of thisprocess, that is to say the edge preparation of a multiplicity of tools,the result of a respective edge processing operation is regularlymonitored. The expression “regularly” refers here to the fact that theedge processing operation itself is monitored by the describedcomparison in each case after a defined number of edge processingoperations, for example after 3 to 5 rounding operations (tools). Inprinciple, it is also possible, and provision is also made for this, tocarry out the measurement and monitoring and also to log the data ateach tool to be processed.

The edge preparation provided is in particular a rounding operation.Alternatively, a bevel is provided using this method. The invention isexplained in more detail below with reference to the rounding operation.The advantages and method features cited also likewise apply to theprovision of a bevel.

According to an expedient configuration, wear of the preparation tool,designated below as a rounding tool, is deduced on the basis of theprogression of the difference between actual value and reference value.Online monitoring of the wear of the rounding tool is therefore alsomade possible by this measuring method. When wear which exceeds anadmissible tolerance value is detected, provision is accordingly alsomade for a desired control value for the rounding tool to be correctedin a control unit of the machine tool. The wear is therefore taken intoaccount for the infeed movement of the rounding tool in order to ensurethe desired result, that is to say the desired material removal, forsubsequent rounding operations.

In an expedient configuration, the preparation tool is in this case abrush and furthermore provision is made in particular for the sensor tobe a probe. Such probes are present in modern processing machines, andtherefore no additional measuring devices have to be attached to aconventional processing machine.

As an alternative to the brush, other preparation tools or preparationmethods can also be provided, such as, for example, a grinding tool or ablasting method, in which the edge to be processed is processed in a wetblasting process, with abrasive particles if required.

The processing machine is preferably a multi-axis, for example 5- or6-axis, CNC machine. Such machines are distinguished by universal usefor the most varied tool processing operations. In particular, suchmachines are also used as universal machines for the further productionprocesses, such as, for example, grinding, etc. It is therefore alsopossible to carry out a plurality of production steps, in particular allthe production steps, such as the flute grinding or the end pointgrinding for producing the tool, without resetting the tool on theprocessing machine.

In a preferred development, in the event of an inadmissible deviationfrom the desired value being detected on account of wear of the roundingtool, a rounding operation is carried out again before the tool isunclamped. However, this is expediently avoided by a timely correctionof the desired control value for the rounding tool.

The present invention further addresses such needs by providing aprocessing machine for carrying out the methods described herein. Themachine includes a clamping unit for clamping the tool in place, apreparation tool for carrying out the edge processing operation, asensor for recording the position of the cutting edge, and a controlunit structured to monitor the edge processing operation on the basis ofa comparison between the reference value and the actual value.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is explained in more detailbelow with reference to the drawings, in which:

FIG. 1 shows a greatly simplified illustration of a processing machinefor carrying out edge rounding on a tool; and

FIG. 2 shows a greatly simplified schematic illustration of a cuttingedge before and after the edge rounding.

Equivalent parts are provided with the same reference numerals in thefigures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to FIG. 1, a processing machine 2 has a clamping unit 4 whichis designed for clamping a tool 6 in place. The processing machine 2 isshown in its entirety in FIG. 1 by the dot-dash line. Furthermore, theprocessing machine 2 comprises a tool unit 8 for the defined guidance ofa tool, in particular a rounding tool, which in the exemplary embodimentis designed as a brush 10. Finally, the processing machine 2 comprises acontrol unit 12 which controls the individual processes of theprocessing machine 2. A sensor designed in particular as a probe 14 isarranged on the tool unit 8. The individual components of the processingmachine 2, which in particular is designed as a CNC machine tool, areadjustable in a controlled manner along various axes, as indicated bythe arrows. In addition to linear adjustments in the direction of axes,rotary adjustments about axes of rotation are also possible. Theindividual adjusting movements can be superimposed in a suitable mannerif required.

To carry out the actual rounding operation, first of all, in a firststep, the probe 14 is brought up to a cutting edge 16 (shown in solidlines in FIG. 2), in particular a main cutting edge of the tool 6. Inthis initial state, the cutting edge 16, as shown, is still of extremelysharp design. As soon as the probe 14 touches the tip of the cuttingedge 16, this position is established as a reference position. Thecorresponding measured values define reference values of the referenceposition.

The reference position is expediently recorded at an appropriate pointon the main cutting edge or also on a secondary cutting edge of the tool6. The position is preferably merely recorded at one point, since therounding operation over the cutting edge length leads within sufficienttolerances to identical material removal d.

The probe 14 is then retracted again and the brush 10 for carrying outthe rounding operation is advanced to the tool 6 in a manner known perse. A desired control value, up to which the brush 10 is advanced to thetool 6, is stored in the control unit 12.

After the rounding process is carried out, which is carried outaccording to a process sequence stored in the control unit 12, the probe14 is again brought up to the then rounded cutting edge 16 (shown indashed line in FIG. 2). The (rounded) position, then recorded by theprobe 14, is evaluated as an actual position and the associated actualvalue is compared with the reference value recorded beforehand. Thedifference between the actual value and the reference value in this casedetermines the material removal d effected during the roundingoperation. If material removal d is within a desired range, that is tosay corresponding to a desired value with predetermined tolerances of,for example, ±5%, the rounding operation is all right. In a preferredconfiguration, if the material removal d effected is too little, arounding operation is carried out once again by advancing the brush 10again.

Preferably provided within the control unit 12 is a comparison modulewhich continuously compares the recorded reference and actual valueswith one another and deduces the wear of the brush 10 on the basis ofthe progression of the difference between the reference values andactual values (during successive rounding operations on various tools6). If the wear exceeds a predetermined tolerance value, the desiredcontrol value stored in the control unit is accordingly corrected.During the next rounding process, the brush 10 is then brought up to thetool in accordance with the new desired control value. As a result ofthis measure, online process monitoring is made possible and providedoverall in a continuous manner during the rounding operation.

Instead of carrying out the rounding operation by means of a brush 10,other rounding tools, such as, for example, blasting methods, etc., canalso be used. The rounding operation itself, with the online processmonitoring described, can be carried out on a special processing machine2 provided only for the rounding.

Further measures, such as, for example, coating measures, etc., can alsobe carried out if required.

The method described here and the processing machine 2 with the controlalgorithm stored in the control unit 12 in accordance with the methodare distinguished by reliable edge rounding and online monitoring of thesame during a multiplicity of successive edge rounding operationswithout the need for a separate external measuring operation forrecording the result of the respective edge rounding operation.

1. A method for providing an edge preparation on a cutting edge of atool by means of an edge processing operation, the method comprising:clamping the tool in a processing machine for providing the edgepreparation; recording as a reference value the position of the cuttingedge to be processed by means of a sensor arranged on the processingmachine; carrying out an edge processing operation by means of apreparation tool; recording the position of the cutting edge again bymeans of the sensor arranged on the processing machine and storing theposition as an actual value; monitoring the edge processing operation onthe basis of a comparison between the reference value and the actualvalue; and comparing the actual value with a desired value for materialremoved on the cutting edge.
 2. The method of claim 1, wherein aplurality of tools are successively processed on the processing machineand wherein wear of the preparation tool is deduced on the basis of theprogression of the difference between actual value and reference value.3. The method of claim 2, wherein when wear of the preparation tool isdetected, a desired control value for the preparation tool is correctedin a control unit of the processing machine.
 4. The method of claim 1,wherein desired value for the material removal is within the range of 3μm to 200 μm.
 5. The method of claim 1, wherein the sensor is a probe.6. The method of claim 1, wherein the preparation tool comprises abrush.
 7. The method of claim 1, wherein the processing machinecomprises a 5-axis CNC machine.
 8. The method of claim 1, wherein anedge preparation is carried out again in the event of an inadmissibledeviation from the desired value.
 9. A processing machine for carryingout the method of claim 1, the processing machine comprising: a clampingunit for clamping the tool in place; a preparation tool for carrying outthe edge processing operation; a sensor for recording the position ofthe cutting edge; and a control unit structured to monitor the edgeprocessing operation on the basis of a comparison between the referencevalue and the actual value.